Quasi-3D numerical modeling of shallow-water circulation

A quasi-three-dimensional numerical model composed of two coupled modules has been developed for computing circulations in shallow waters. The depth-averaged flow is computed in one of the modules, and the vertical distribution of the flow velocities is determined in the other. A simple algebraic formulation is assumed for the vertical eddy viscosity. Based on measurements of velocity profiles in a wind-water flume, it was found that the vertical eddy viscosity should be scaled using the larger value of the bed- and surface-friction velocities. For the cases considered, computations using the k-epsilon model supported the results. Secondary currents caused by curvature effects and Coriolis force in open channel flow can be simulated by using the model. The model was also applied to compute circulations in a model harbor basin where measurements of velocities were available. The advective terms in the equations of motion are shown to be important to model the three-dimensional features of these flows.